1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the present invention relates to the structure and use of bipolar forceps and other instruments for coagulating, cutting, and necrosing tissue.
Electrosurgery refers broadly to a class of medical procedures which rely on the application of high frequency electrical energy, usually radiofrequency energy, to patient tissue to achieve a number of possible effects, such as cutting, coagulation, hyperthermia, necrosis, and the like. Of particular interest to the present invention, bipolar electrosurgical devices rely on contacting electrodes of different polarity in close proximity to each other against or into tissue. For example, bipolar forceps 100 (FIGS. 1 and 2) have been used for cutting and coagulating tissue, where the opposed jaws 102 and 104 of the forceps are connected to different poles of an electrosurgical power supply. The high frequency electrical current thus flows from one jaw to the other through the tissue present therebetween. Use of such bipolar forceps is effective for a number of purposes and advantageous in that its effect is generally limited to the tissue held between the jaws. Heating, however, is not totally limited to such intermediate tissue, and in some instances heating of adjacent tissues can be problematic. Such heating occurs because the current flows not only between the jaws but also laterally outward, as shown by flux lines F in FIG. 1B.
Various improvements to bipolar forceps have been proposed. For example, the placement of pins or other tissue-penetrating elements onto the tissue-engaging surface(s) of either or both jaws has been suggested for a variety of purposes. Regardless of the intended purpose, the placement of tissue-penetrating elements on the jaw(s) can marginally focus the current density and somewhat lessen heating of adjacent tissues. Such prior designs employing tissue-penetrating elements, however, still cause unwanted heating of adjacent tissues in at least certain circumstances.
A second problem with conventional bipolar forceps is limited power delivery. With conventional forceps, jaws having a length of about 20 mm and a width of about 5 mm can usually deliver only 25 W of power without causing charring of the tissue. Charring greatly increases electrical resistance through the tissue and can result in premature termination of the treatment. With such a low power level, the time to fully coagulate the tissue can be excessive.
It would therefore be desirable to provide still further improved bipolar forceps and other electrosurgical device designs. In particular, it would be desirable to provide bipolar forceps which provide a very high degree of focused heating, i.e., provide heating of tissue between the jaws with minimized heating of tissue adjacent to the jaws. It would be further desirable to provide bipolar forceps which can deliver higher current flows and densities to the tissue being treated without charring the tissue and terminating the current flow. Such device designs should be relatively simple and easy to fabricate. The devices and methods should be compatible with conventional electrosurgical power supplies and usable in a wide variety of procedures, including cutting, coagulation, and necrosis, where the localized and specific heating of patient tissues is desired. At least some of these objectives will be met by the invention described hereinafter.
2. Description of the Background Art
Radio frequency power apparatus and methods for delivering radio frequency energy to tissue via bipolar surgical instruments are described in co-pending application Ser. No. 09/808,096 filed Mar. 13, 2001, assigned to the assignee of the present application. Bipolar forceps having penetrating elements on opposed jaws thereof are described in U.S. Pat. Nos. 5,527,313 and 5,217,460; Soviet Union Patent Publication SU 197711; and French Patent No. 598,149. Bipolar electrosurgical instruments having laterally spaced-apart electrodes on opposed jaws are described in U.S. Pat. Nos. 5,833,690; 5,702,390; 5,688,270; and 5,403,312. A blood vessel coagulation device having electrode arrays on opposed jaws of forceps is described in U.S. Pat. No. 5,151,102. Other bipolar electrosurgical devices are described in U.S. Pat. Nos. 5,797,941; 5,665,085; 5,662,680; 5,582,611; 5,445,638; 5,441,499; 5,383,876; 5,403,312; 5,098,431; and 4,043,342. A radiofrequency tumor heating device comprising parallel electrode arrays of opposite polarity is described in U.S. Pat. No. 4,016,886.
The full disclosures of each of the above references are incorporated herein by reference.
The present invention provides improved bipolar surgical instruments, such as forceps, graspers, or the like, which comprise a pair of opposed jaws at the distal end of a shaft. The present devices may be usable in a wide variety of procedures, including open surgical and laparoscopic surgical procedures, and are designed for one-handed operation by a user. The present invention is directed at a unique electrode configuration on either or both of the jaws which will provide improved current focussing characteristics and lessened heating of adjacent tissues. In particular, electrode members on either or both of the jaws will be laterally spaced apart from each other when the jaws are closed so that current will flow from one electrode to the other with minimum current flow outside of the region defined between the electrodes. Optionally, a pair of electrodes can be provided on each jaw with a positive and negative electrode on one jaw and a positive and negative electrode on the other jaw, with the two positive electrodes and the two negative electrodes being aligned with each other when the jaws are closed to define the desired focussed current flow.
At least one of the electrode members will include tissue-penetrating elements. Usually a first line of electrically coupled tissue-penetrating elements will be provided on a first electrode member, and a second line of electrically coupled tissue-penetrating elements will be provided on a second electrode member. Third and fourth lines of electrically coupled tissue-penetrating elements will preferably be provided when third and fourth electrode members are provided on the instrument. The first and second lines (and optionally third and fourth lines) of tissue-penetrating elements will be electrically isolated from each other to permit energization in a bipolar manner, i.e., each line of electrically coupled tissue-penetrating elements may be separately connected to the opposite pole of a conventional electrosurgical power supply. An exemplary radio frequency electrosurgical generator for use with the present invention is described in co-pending application Ser. No. 09/808,096, assigned to the assignee herein. The shaft includes or comprises an actuating mechanism for moving the jaws between opened and closed configurations, where the lines of tissue-penetrating elements lie parallel to and spaced-apart from each other when the jaws are closed. In this way, the jaws can be closed on a target tissue structure, such as a fallopian tube, artery, vein, other hollow organs, and the like, in order to penetrate the lines of elements into the tissue. By then applying high frequency electrical energy to the lines in a bipolar manner, current flux will be focused to within that portion of the tissue which lies between the adjacent lines, with minimum heating of tissue outside of the parallel lines. Usually, but not necessarily, the lines will both be straight. Alternatively, the lines could be nonlinear, e.g., curved, serpentine, zig-zag, or the like, so long as the patterns are similar and the lateral spacing between adjacent points on the lines remains substantially constant. Preferably, the spacing between the adjacent lines of tissue-penetrating elements will be in the range from 0.5 mm to 10 mm, more preferably from 2 mm to 5 mm.
Preferably, at least some of the tissue-penetrating elements on the electrode member(s) will be retractable relative to a surface of the jaw upon which they are mounted. Usually, the tissue-penetrating elements will be arranged to reciprocate in and out of either or both of the jaws so that the jaws can be clamped over opposed surfaces of a target tissue region or mass with the elements retracted and the elements then penetrated into the tissue while the tissue remains clamped. In some instances, lines of reciprocating tissue-penetrating elements will define at least two and sometimes all of the electrode members. In other instances, they will form only one of the electrode members and/or they will be combined together with one or more elongate surface electrodes which engage but do not penetrate into the tissue.
The lines of tissue-penetrating elements may be on the same jaw or on different jaws. When the lines are on the same jaw, it is necessary to provide insulation so that each line is electrically isolated from the other, while the plurality of tissue-penetrating elements in an individual line remain electrically coupled. Electrical conductors will be provided within the shaft in order to permit attachment of each line to opposite polarity connections on an electrosurgical power supply. When present on different jaws, the lines of tissue-penetrating elements may be isolated from each other by maintaining appropriate electrical isolation between the jaws and/or at either or both ends of the tissue-penetrating elements.
The tissue-penetrating elements may have a wide variety of different configurations. Most commonly, they will be in the form of a pin or other rod-like tissue-penetrating electrode, usually having a sharpened distal end to facilitate penetration into tissue. Alternatively, an appropriate cutting current could be applied to the electrodes in order to facilitate tissue penetration while the jaws are being closed. Each line of tissue-penetrating elements may contain from 3 to 50 individual elements, usually from 6 to 25. The elements may extend over a length on the jaw(s) in the range from 1 mm to 50 mm, usually from 5 mm to 25 mm, with spacing between individual elements being in the range from 0.25 mm to 5 mm, usually from 0.5 mm to 2 mm. The distance between adjacent lines of tissue penetrating elements will usually be in the range from 0.5 mm to 10 mm, usually from 2 mm to 5 mm. The height of the tissue-penetrating elements (corresponding to the depth of tissue penetration) will usually be in the range from 1 mm to 10 mm, preferably from 2 mm to 5 mm, while the diameter of the elements will typically from 0.1 mm to 2 mm, usually from 0.5 mm to 1 mm.
In a more specific aspect of the present invention, the bipolar surgical instrument will comprise a shaft and a pair of opposed jaws, as generally described above. A first electrode member comprising a first line of tissue-penetrating elements will be disposed on one of the jaws and a second electrode member comprising a second line of tissue-penetrating elements will be disposed on one of the jaws. Either electrode members may be on the same jaw or on opposed surfaces of the two jaws. The first and second electrode members are electrically isolatable and laterally spaced-apart from each other. The bipolar device further includes a linkage attaching at least one of the jaws to the shaft. The linkage maintains opposed surfaces of the jaws in a generally parallel orientation as the jaws are moved between an opened and closed configuration by the linkage.
The linkage may be a parallelogram movement linkage, wherein actuation of the linkage by a clamp trigger on a handle attached to the proximal end of the shaft allows for parallel opening and closing of the jaws. The lines of tissue-penetrating elements will typically project toward the opposed jaw and lie parallel to each other as the jaws are opened and closed. The lines of tissue-penetrating elements (typically in the form of pins, needles, or other self-penetrating rods) may also be advanceable and retractable relative to a surface of the jaw upon which they are mounted by a knob on a handle attached to the proximal end of the shaft. Usually the knob will reciprocate the tissue-penetrating elements in and out of the jaw itself. In addition to protecting the tissue-penetrating elements and facilitating grasping of tissue (without the tissue-penetrating elements interfering when they are in the retracted position), reciprocation of the elements has the additional advantage of cleaning the tissue-penetrating elements during use. Frequently, charred tissue coagulated blood and/or other debris may foul the tissue-penetrating elements reducing their ability to effectively deliver high frequency electrical energy to the tissue. Reciprocation of the elements within the structure of the instrument will tend to shear debris from the surfaces of the tissue-penetrating elements (electrodes) to decrease surface resistance and impedance.
The instrument of the present invention may further comprise a cutting blade, knife, or other tissue-cutting structure disposed on one of the jaws. The cutting blade is actuatable to cut along a line between the first and second lines of tissue-penetrating elements by a cutting trigger on a handle attached to the proximal end of the shaft. In this way, the jaws can be clamped on tissue by pulling the clamping trigger, the tissue-penetrating elements penetrated into the tissue by knob advancement, the tissue treated electrosurgically by knob depression, and the tissue then cut between the two desiccated tissue regions by pulling the cutting trigger.
Optionally, either or both of the jaws may be perforated or otherwise provided with passages in order to permit the release of steam which is a byproduct of tissue heating. A rotational grip may also be attached between the proximal end of the shaft and a handle so as to allow for rotation of the shaft and the jaws relative to the handle. The rotational grip will usually permit rotation of the shaft and jaws up to about 90xc2x0 in a clockwise and/or counter-clockwise direction from a centered position so as to facilitate loading and clamping of tissue by the jaws and to further minimize or prevent tissue deflection when the jaws are closed. A tissue stop may also be attached to one of the jaws of the present invention to prevent loading of tissue beyond the tissue-penetrating elements so as to ensure that only a target tissue region is clamped and treated.
In a more specific aspect of the method of the present invention, tissue is grasped between a first jaw and a second jaw, wherein opposed surfaces of the jaws are maintained in a generally parallel orientation. A first line of tissue-penetrating elements on one of the jaws and a second line of tissue-penetrating elements on one of the jaws is advanced through a surface of the jaw upon which they are mounted and into the tissue after grasping the tissue between the jaws. Clamping the tissue prior to advancing the tissue-penetrating elements protects the tissue-penetrating elements, i.e., from bending, and facilitates proper alignment of the tissue-penetrating elements into the tissue. The lines of tissue-penetrating elements will be parallel to and laterally spaced-apart from each other, generally as described above. A high frequency energy is then applied between a first line of tissue-penetrating elements on one of the jaws and a second line of tissue-penetrating elements on the same or a different jaw after advancing the lines of tissue-penetrating elements into the tissue.
A high frequency energy will preferably be applied to the tissue at a level and for a time sufficient to desiccate substantially all the tissue between the lines without causing substantial damage to other tissue, i.e., tissue outside of the lines. As described in greater detail in co-pending application Ser. No. 09/808,096, assigned to the assignee herein, the high frequency energy will be applied at a frequency in the range from 100 kHz to 2 MHz, preferably from 400 kHz to 500 kHz. The energy will be applied at a power from 5 W to 150 W, preferably from 10 W to 80 W, and for a time less than 5 minutes, usually from a range of 10 seconds to 1 minute. The power level may be increased at a predetermined rate from 1 W/sec to 100 W/sec, preferably from 1 W/sec to 10 W/sec. Usually, the high frequency energy will be terminated when an impedance of the tissue is in the range from 50 ohms to 1000 ohms, preferably from 250 ohms to 750 ohms.
The method of the present invention may further comprise rotating the jaws up to about 90xc2x0 in a clockwise and/or counter-clockwise direction from a centered position prior to grasping the tissue between the jaws. This facilitates loading and clamping of tissue by the jaws and further minimizes or prevents any tissue deflection when the jaws are closed. Further, the grasping force applied to the tissue by the first and second jaws may be limited so that only sufficient force to clamp the tissue is applied. The method may also include cutting the tissue along a line between the first and second lines of tissue-penetrating elements after the tissue has been substantially desiccated. It will be appreciated that the tissue is still grasped between the jaws and the tissue engaged by the tissue penetrating elements so as to facilitate proper alignment of the desiccated tissue during cutting. The lines of the tissue-penetrating elements are then retracted prior to disengaging the jaws after treatment to prevent any tearage of tissue.